In recent years, wandering of elderly people with dementia and accidents involving stumbling or falling around the bed have become a social problem, and countermeasures to these problems are required. In addition, it is expected that a quicker response in case of emergency can be made by monitoring the movement of users who are present on the bed for a long time, such as the elderly or the patient shortly after surgery, based on the load information of the bed.
For this purpose, for example, in Patent Literatures 1 to 3, a load detector is provided on a leg portion of a bed or between a leg portion and a floor to directly measure the load, or a torque sensor for indirectly measuring the load is provided in the elevating mechanism of the floor portion. Further, in Patent Literatures 4 and 5, a load detector is provided in a frame of a bed.